Morrison L J, Chamot-Rooke J, Wysocki V H
Department of Chemistry and Biochemistry, The Ohio State University, 484 W. 12th Ave, Columbus, OH 43210, USA.
Analyst. 2014 May 7;139(9):2137-43. doi: 10.1039/c4an00064a.
The interplay between the entropically and enthalpically favored products of peptide fragmentation is probed using a combined experimental and theoretical approach. These b2 ion products can take either an oxazolone or diketopiperazine structure. Cleavage after the second amide bond is often a favorable process because the products are small ring structures that are particularly stable. These structures are structurally characterized by action IRMPD spectroscopy and semi-quantified using gas-phase hydrogen-deuterium exchange. The formation of the oxazolone and diketopiperazine has been thought to be largely governed by the identity of the first two residues at the N-terminus of the peptide. We show here that the length of the precursor peptide and identity of the third residue play a significant role in the formation of the diketopiperazine structure in peptides containing an N-terminal asparagine residue. This is additionally the first instance showing an N-terminal residue with an amide side chain can promote formation of the diketopiperazine b2 ion structure.
采用实验与理论相结合的方法，对肽片段化过程中熵驱动产物和焓驱动产物之间的相互作用进行了探究。这些b2离子产物可以采取恶唑酮或二酮哌嗪结构。第二个酰胺键之后的裂解通常是一个有利的过程，因为产物是特别稳定的小环结构。通过红外多光子解离光谱对这些结构进行了结构表征，并利用气相氢氘交换进行了半定量分析。恶唑酮和二酮哌嗪的形成在很大程度上被认为受肽N端前两个残基的特性所支配。我们在此表明，前体肽的长度和第三个残基的特性在含有N端天冬酰胺残基的肽中二酮哌嗪结构的形成中起着重要作用。这也是首次表明具有酰胺侧链的N端残基可以促进二酮哌嗪b2离子结构的形成。
